India's most prominent anti-corruption crusader has emerged from a New Delhi jail to cheers of "Long live Mother India" and a shower of rose petals as he prepares to begin a 15-day public hunger strike.

Anna Hazare's standoff with authorities has stoked anger at official corruption and put the prime minister, Manmohan Singh, on the defensive as the government fights off a series of scandals.

Nearly 2,000 men, women and schoolchildren gathered outside Tihar jail on Friday morning to catch a glimpse of the 73-year-old activist who has used the tactics of Mahatma Gandhi in his fight to force the government to adopt his proposals for an anti-corruption law.

The crowd, some standing on top of parked cars, erupted in applause as he walked out of jail.

"Long live the revolution," Hazare said before climbing into the back of a truck that led a slow-moving procession to the parade ground in the centre of Delhi where he plans to fast. Hundreds followed on foot.

"The government will have to bend in front of this movement," said one of Hazare's supporters, Prakash Khattar, a bank employee. "This is just the trailer, the film is yet to start."

Police briefly arrested Hazare on Tuesday after he declared his intention to hold a public hunger strike in defiance of restrictions placed on the demonstration. He began his fast in jail and refused to leave when a release warrant was granted, demanding the right to hold a long public hunger strike. A compromise was reached on Thursday, but Hazare opted to stay in jail for another day while the protest venue was prepared.

Hazare wants the government to pass his version of a proposed bill and create a powerful ombudsman to police top officials. Activists have criticised the version of the bill tabled in parliament as too weak.

Government officials have accused Hazare of twisting time-honoured protest tactics to subvert the legislative process and force elected officials to bow to his own agenda.

One poster held aloft outside the jail showed cartoons of government ministers looking like donkeys with fangs and with dollar signs emblazoned on them.

"I am Anna, you are Anna. Now the whole country is Anna," read another poster.

One of the crowd, Asha Bansal, said Hazare had "come like a god to save this country. Everyone is so sick of these politicians who are only out to make money".

Hazare, a retired army driver, has transformed himself into the most prominent social activist in his home state of Maharashtra in recent decades. He has held a series of hunger strikes to force the state government to enact reforms and on at least one occasion forced it to capitulate by taking a vow of silence.

He came to national prominence in April when he held a four-day hunger strike to demand that the government draft legislation for an anti-corruption watchdog. This week, despite being inside a jail and seen only in a brief YouTube video, he has become a symbol of national anger about corruption.

After his arrest on Tuesday, thousands of mainly middle-class people marched in cities across India in support of him. As hundreds of demonstrators gathered outside the jail, authorities capitulated to many of his demands and granted him permission for a 15-day public protest.

"I have full trust in his ability to bring change," said Khattar.

Others were less optimistic. The business daily Mint said in a front-page commentary on Friday that the protests were unlikely to spark major change in Indian governance.

India's anti-graft campaigner Anna Hazare leaves jail to carry on his anti-corruption fast, as crowds of supporters greet him. Nearly 2,000 men, women and schoolchildren gathered outside Tihar jail to catch a glimpse of the activist who has used the tactics of Mahatma Gandhi in his fight to force the government to adopt his proposals